RFR: JDK-8065215 Print warning summary at end of configure

[Tim Bell]

Magnus:

>> Warnings in configure tends to just fly by quickly and be buried in 
>> the verbose autoconf output.
>>
>> We could with a simple trick repeat all those warnings (if any) at 
>> the end of configure, where they will be more easily spotted.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8065215
>> WebRev: 
>> http://cr.openjdk.java.net/~ihse/JDK-8065215-print-warning-at-end-of-configure/webrev.01
>
> As an example, the last part of the configure output might look like 
> this:
>
> Tools summary:
> * Boot JDK:       java version "1.8.0" Java(TM) SE Runtime Environment 
> (build 1.8.0-b132) Java HotSpot(TM) 64-Bit Server VM (build 25.0-b70, 
> mixed mode)  (at /localhome/java/jdk-8-fcs-bin-b132-linux-x64)
> * Toolchain:      gcc (GNU Compiler Collection)
> * C Compiler:     Version 4.8.2 (at /usr/bin/gcc)
> * C++ Compiler:   Version 4.8.2 (at /usr/bin/g++)
>
> Build performance summary:
> * Cores to use:   14
> * Memory limit:   28134 MB
>
> WARNING: The result of this configuration has overridden an older
> configuration. You *should* run 'make clean' to make sure you get a
> proper build. Failure to do so might result in strange build problems.
>
> The following warnings were produced. Repeated here for convenience:
> WARNING: Option --with-custom-make-dir is deprecated and will be ignored.

Looks good to me.

/Tim